Solvent‐Free Oxidation of Benzyl Alcohol Using Modified Zeolitic Imidazolate Frameworks‐8 (ZIF‐8) Catalysts

Abstract Selective oxidation of alcohols towards carbonyl‐based products, such as aldehydes, is a subject of significant interest in the field of catalysis. Herein, a Zn‐based MOF with 2‐methylimidazolate linker (ZIF‐8) is modified and introduced as catalysts in a selective oxidation of alcohol with benzyl alcohol as the model of the reaction. Modification of ZIF‐8 includes the inclusion of Co(II), Cu(II) or Ni(II) ions as partial replacements for the original Zn(II) metal ions during the synthesis process. The resulting modified ZIF‐8 displays similar PXRD patterns to that of ZIF‐8, indicating no alteration of structures after the introduction of Co(II), Cu(II) or Ni(II) ions. However, the addition of Co(II) was found to modify the resulting ZIF‐8 composition to a higher extent compared to that of Cu(II) and Ni(II) ions. The catalytic test of benzyl alcohol oxidation was performed in a solvent‐free condition with TBHP as the oxidant. Reaction optimization includes reaction temperature, mass of catalysts, TBHP concentration, and reaction time. Among all the catalysts employed in the oxidation of benzyl alcohol, Co(II)‐ and Cu(II)‐modified ZIF‐8 show the highest catalytic activity with 64 % and 62 % conversion, respectively. Furthermore, the catalyst leaching and recyclability tests show that the reactions proceed in heterogeneous systems.